Cu(In,Ga)Se2-based solar cells prepared from Se-containing precursors

• A two-stage method has been developed to prepare Cu (In,Ga)Se2 films.
• The properties of Cu (In,Ga)Se2 film with various [Cu]/[In + Ga] ratios were investigated.
• The secondary Cu2−xSe phase tends to segregate at film surface.
• The mean conversion efficiency close to 10% was achieved.

In this paper, we prepared the CIGS thin films with various [Cu]/[In + Ga] ratios by selenization of Cu0.8Ga0.2 and In2Se3 precursor films. The properties of Cu(In,Ga)Se2 film and related solar cell were investigated. Raman spectra confirm that the secondary Cu2−xSe phase tends to segregate at film surface. SEM results show that the grain-size improves noticeably with the increase of the [Cu]/[In + Ga] ratios. For Cu-rich CIGS films, the performances of the related solar cells were damaged greatly and good photovoltaic characteristics cannot be obtained. For near-stoichiometric and Cu-poor films, the mean conversion efficiency close to 10% was achieved over a wide range of composition.